Study On Meso-Structure Movement And Deformation Failure Mechanism Of Cold Recycled Mixture Under Repeated Load

The cold regeneration of emulsified asphalt plant is a kind of pavement regeneration technology which can be used to recycle old materials and can be constructed under normal temperature.There are many studies on the study of common asphalt mixture under repetitive loading,and the research is mature,the study on the change of the microstructure of the emulsion bituminous mixture is relatively small.Based on the above research background,taking digital image processing and computational simulation techniques as examples,taking the variation law of meso parameters of emulsified asphalt cold recycled mixture as the main line of study.From the perspective of macroscopical and macroeconomic,the multi-angle investigation of the mixture was carried out to quantitatively evaluate the meso-structure movement of the mixture under repeated load.The model of response relationship between meso-structure index and rut depth was established.The mixed material mesoscopic structure and rutting depth data were used to construct the hybrid motion recognition model.It is significant to rationally formulate the time of cold reclaimed pavement maintenance and improve the road performance of the mixture.The main research results and contents are as follows:1.Based on the image processing technology,the mesoscopic structure features of the mixture were extracted,and the movement of the mesostructures under different loadings was systematically evaluated.This paper makes a statistical analysis of the contact characteristics of the material distribution and aggregates of the section images.Based on the fractal theory,the variation of aggregate complexity is further studied.The area ratio of aggregate in the Delaunay triangulation surface area was used to study the in-line extrusion variation in the mixture.Under the background of this study,it is found that there is a turning point in the movement of the mesostructure structure of the mixture.The movement of the mixture is divided into three stages:initial compaction stage of the aggregate,relative compaction stage of the aggregate and over-pressure destruction stage of the aggregate.2.Through the identification statistics of meso-structure index of mixture under different loads and the corresponding collection of rut depth data,the function equations of each meso index and rut depth are determined.Making the meso-index of mixture as input parameter and rut depth as output parameter,the prediction model of rut depth under multi-indexes was built based on SVM and BP neural network.The results show that the SVM model has a good fitting effect with a maximum error of only 9.9%.The establishment of this model can effectively reveal the relationship between the mesoscopic structure and the depth of rutting.3.The mixture motion state has a strong correlation with its fine structure and mechanical properties.The study adopted the index of mixed material and rutting depth as the distinguishing parameter of its motion state.Based on the probabilistic neural network and support vector machine theory,the hybrid motion identification model is constructed.The results show that the recognition accuracy of support vector machine model is higher and the stability is better.The established model can be used in the actual pavement mixture motion state recognition,thus the optimal curing time is determined for the actual pavement condition,and the scientific model support is provided for the road condition evaluation.4.Based on the two-parameter Weibull distribution theory and cellular automata model,the development and evolution of cracks in the mixture of different homogeneity are simulated.The results showed that when the homogeneity of the mixture was high,the crack of microdamage was less before the macro crack occurred.The distribution of macro cracks is relatively concentrated.When the homogeneity degree was reduced,there were many cracks in microcracks before the macro crack occurred.The distribution of macro cracks is disordered.The results of this study are of great significance to the mechanical failure model of the mixture in the following construction.